I recently recorded a Facebook Live video critiquing a new study that suggested vitamin D does not prevent bone fracture. This study was published in The Lancet in October 2018 and was clearly flawed in many ways. For those of you who did not catch my video commentary on the shortcomings of this study, I summarize them here.

Not all studies are created equal

I’ve been looking at the research on vitamin D for almost 30 years. It’s been clear for quite some time that you can reduce fracture risk with vitamin D if you obtain the therapeutic level of 32 ng/mL in your blood. So why would the new study claim that vitamin D doesn’t work to lower fracture risk?

To put it simply, the new study used a lot of vitamin D data that just wasn’t very good to start with. As a meta-analysis, it mined data from 80 studies on vitamin D from the past 20 to 30 years. But the problem is that most of these studies were flawed in the following ways:

They were mostly evaluating low doses of vitamin D (400–800 IU) that we know to be too low to affect fracture risk.

Many of them were too small and too short in duration to really assess the effectiveness of an intervention with vitamin D.

To be valuable, the study must document not only how much the participants took, but also whether they reached the therapeutic level. The vast majority of the studies didn’t report what blood level their participants reached—so none of them can say for sure that their participants had adequate vitamin D levels, particularly since few of them assessed the starting blood levels.

In those studies that did give higher doses of vitamin D, most of the time it was supplied in a single bolus of 100,000–300,000 units — which has been shown to be ineffective. To be most effective, the vitamin D dose should be given daily and it should always be given in the form of a natural vitamin D3 (cholecalciferol), not vitamin D2 (ergocalciferol).

The standard treatment for vitamin D deficiency uses 7,000 IU of vitamin D daily for 8 weeks, followed by testing of the new vitamin D level. Then the appropriate, long-term dose of vitamin D is determined. This is a dose that would provide at least a 32 ng/mL blood level of vitamin D, the minimum needed for health, with the goal of reaching an ideal range from 50–60 ng/mL.

When you look at the data the study used, it’s pretty clear that this recent metanalysis is seriously flawed, and that the author’s conclusion that vitamin D is of no use in fracture prevention is both irresponsible and harmful.

So don’t be fooled — the value of vitamin D, established over many years of good research, is no different in 2018 than it was in 2008, when I first published my research review article on the subject.